FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See section 10, rule 13)
“COGENERATION SYSTEM”
PANASONIC CORPORATION, a Japanese Corporation
of 1006, Oaza Kadoma, Kadoma-shi,
Osaka 571-8501, Japan
The following specification particularly describes the invention and the
manner in which it is to be performed.

DESCRIPTION
Title of the Invention: Cogeneration System
Technical Field
[0001] The present invention relates to a cogeneration system which uses a solid oxide
fuel cell (SOFC) as a base power supply.
Background Art
[0002] To support popularization of mobile communication in developing countries, it
is necessary to put ininfrastructure in place in a base station, or the like. However, in
most districts of the developing countries, utility power infrastructures have not been put
in place yet, and therefore, it is difficult to supply electric power stably to the base station.
Under the circumstances, in provision of the base station in the developing countries,
development of a self-sustainable power supply in the base station, improvement a fuel
efficiency of the self-sustainable power supply, easiness of maintenance of the
self-sustainable power supply, and the like are important aims to be attained.
[0003] Accordingly, in recent years, the use of a fuel cell as a backup power supply in
the base station has been practiced. For example, as the system using the fuel cell as the
backup power supply, there is US T-Mobile, etc. (see Patent Literature 1). As this
system, a backup system using PEFC (polymer electrolyte fuel cell) is disclosed.
[0004] Another fuel cell system is disclosed, which includes a SOFC unit and an
absorption chiller, and is configured such that the absorption chiller is actuated by
heating a reproduction device of the absorption chiller by a combustion exhaust gas
discharged from the SOFC unit (Patent Literature 2).
Citation Lists
Patent Literature
[0005] Patent Literature 1: US Patent No. 8,005,510 Speciifcation
Patent Literature 2: Japanese Laid-Open Patent Application Publication No.
2006-73416
Summary of the Invention
Technical Problem
[0006] However, in the above stated prior arts, in the system which practices

cogeneration in which an energy efficiency is improved by actuating the absorption
chiller by an exhaust gas generated during power generation in the fuel cell, there is a
problem that water of an amount required for the power generation in the fuel cell cannot
be recovered within the system.
[0007] More specifically, the fuel cell system disclosed in Patent Literature 1 is the
PEFC (polymer electrolyte fuel cell). An operation temperature of the PEFC is low (60
to 80 degrees C), and a refrigeration cycle of the absorption chiller cannot be actuated by
the exhaust gas (combustion exhaust gas) discharged. In other words, the fuel cell
system disclosed in Patent Literature 1 is incapable of implementing cogeneration which
improves the energy efficiency such that the absorption chiller can be actuated by
utilizing the exhaust gas.
[0008] The fuel cell system disclosed in Patent Literature 2 is configured such that a
heat exchanger exchanges heat between the exhaust gas and the water to recover a
moisture from the exhaust gas containing it as steam. However, the combustion exhaust
gas still has high-temperature heat after the absorption chiller is actuated by heating the
reproduction device of the absorption chiller using the heat of of the exhaust gas. Even
after the heat exchanger exchanges heat between the exhaust gas and the water after the
absorption chiller is actuated by utilizing the heat, the resulting temperature of the
exhaust gas is about 100 degrees C at maximum (see [0054] in Patent Literature 2).
[0009] To recover the water of an amount required to actuate the fuel cell system from
the exhaust gas, it is necessary to lower the temperature of the exhaust gas to about 40
degrees C, as will be described in detail later. That is, in the configuration of the fuel
cell system disclosed in Patent Literature 2, the temperature of the exhaust gas cannot be
lowered sufficiently to a temperature at which the water of an amount required to actuate
the fuel cell system can be recovered from the exhaust gas.
[0010] The heat exchanger in the fuel cell system disclosed in Patent Literature 2 is
configured to exchange heat between the exhaust gas and water supplied as tap water,
and the like. In a case where a fuel cell system is provided in an environment in which
water cannot be supplied from outside as described above, the heat exchanger disclosed
in Patent Literature 2 cannot be used.
[0011] In the fuel cell system disclosed in Patent Literature 2, therefore, the water
cannot be supplied in a self-sustainable manner within the system. This fuel cell system

cannot be utilized in a region where no water source is attained.
[0012] The present invention has been developed in view of the above stated problems,
and an object of the present invention is to provide a cogeneration system which is
capable of supplying water in a self-sustainable manner within the system.
Solution to Problem
[0013] To achieve the above described objective, accoridng to the present invention, a
cogeneration system comprises a high-temperature operative fuel cell configured to
generate electric power through a power generation reaction by using a fuel supplied to
the fuel cell and air supplied to the fuel cell; a reformer configured to generate a
reformed gas which becomes the fuel, through a reforming reaction between a raw
material gas supplied to the reformer and a steam supplied to the reformer, by utilizing
power generation reaction heat generated in the high-temperature operative fuel cell and
combustion heat of unconsumed fuel; a vaporizer configured to generate the steam to be
added to the raw material gas supplied to the reformer by utilizing the power generation
reaction heat and the combustion heat; a cooling apparatus configured to cool a target by
consuming a portion of the power generation reaction heat and a portion of heat of an
exhaust gas having the combustion heat which remain after the reformer and the
vaporizer have consumed the heat, and cool the exhaust gas by consuming a portion of
the heat; and a condensation unit configured to cool the exhaust gas after the cooling
apparatus has consumed the portion of the heat owned by the exhaust gas to condense a
moisture contained in the exhaust gas to generate condensed water.
[0014] Therefore, the cogeneration system of the present invention can achieve an
advantage that water can be supplied in a self-sustainable manner within the system.
Advantageous Effects of the Invention
[0015] Therefore, the cogeneration system of the present invention is configured as
described above, and can achieve an advantage that water can be supplied in a
self-sustainable manner within the system.
Brief Description of the Drawings
[0016] [Fig. 1] Fig. 1 is a schematic view showing an exemplary configuration of a
cogeneration system in a base station according to Embodiment 1.
[Fig. 2] Fig. 2 is a schematic view showing an exemplary configuration of the
cogeneration system in the base station according to Embodiment 1.

[Fig. 3] Fig. 3 is a schematic view showing an exemplary configuration of the
cogeneration system in the base station according to Embodiment 1.
[Fig. 4] Fig. 4 is a schematic view showing an exemplary configuration of the
cogeneration system in the base station according to Embodiment 1.
[Fig. 5] Fig. 5 is a schematic view showing an exemplary configuration of a
cogeneration system according to Modified example 1 of Embodiment 1.
[Fig. 6] Fig. 6 is a schematic view showing an exemplary configuration of a
cogeneration system according to Modified example 2 of Embodiment 1.
[Fig. 7] Fig. 7 is a schematic view showing an exemplary configuration of a
total enthalpy heat exchanger in the cogeneration system of Fig. 6.
[Fig. 8] Fig. 8 is a schematic view showing an exemplary configuration of a
cogeneration system according to Modified example 4 of Embodiment 1.
[Fig. 9] Fig. 9 is a view showing an example of supply and generation of
substances in a reforming efficiency and a fuel/oxygen use (utilization) efficiency, in a
cell reaction in which water of 1 mol is generated from hydrogen of 1 mol and oxygen of
0.5 mol in the cogeneration system according to Embodiment 1.
[Fig. 10] Fig. 10 is a view showing an example of supply and generation of
substances in the reforming efficiency and the fuel/oxygen use efficiency, in the cell
reaction in which water of 1 mol is generated from hydrogen of 1 mol and oxygen of 0.5
mol in the cogeneration system according to Embodiment 1.
[Fig. 11] Fig. 11 is a schematic view showing an exemplary configuration of a
cogeneration system according to another embodiment (Embodiment 2).
[Fig. 12] Fig. 12 is a schematic view showing an exemplary configuration of
the cogeneration system according to another embodiment (Embodiment 2).
[Fig. 13] Fig. 13 is a schematic view showing an exemplary configuration of a
present (current) base station.
Description of Embodiments
[0017] (Finding which is the basis of the invention)
As shown in Fig. 13, generally, a present (current) base station includes a base
station shelter 200, a utility power supply (GRID) 201, and a diesel generating apparatus
(DG) 202, and electric power is supplied to the base station shelter 200 from both of the

GRID 201 and the DG 202. Fig. 13 is a schematic view showing an exemplary
configuration of a present (current) base station.
[0018] The base station shelter 200 includes therein BTS (base transceiver system:
communication device) 211, an air conditioner (AC) 212, and a power management
system (PMS) 213 including a storage battery (SB) 219 for backup.
[0019] The PMS 213 converts the electric power (e.g., AC 220V) from the DG 202 and
the GRID 201 into electric power (e.g., DC 48V) for actuating the BTS 211, and supplies
the DC power to the BTS 211. In addition, the PMS 213 manages power for continuous
electric power consumption in the BTS 211, for example, backup performed by SB 219
until the DG 202 is activated in a state in which the electric power is not supplied from
the GRID 201 to the BTS 211.
[0020] The AC 212 adjusts a room temperature so that a temperature in an interior of
the base station shelter 200 does not exceed an operating temperature of the BTS 211.
Specifically, the AC 212 adjusts the room temperature so that the temperature in the
interior of the base station shelter 200 becomes about 35 degrees C.
[0021] The electric power consumption in the base station in the present situatioin will
now be discussed. It is known that the base station is a facility which is lower in energy
efficiency than another facilities on the basis of an index of PUE (power usage
efficiency). The PUE is an index indicating energy efficiency of a data center, a
communication base station, etc., and is derived by dividing total energy consumption by
energy consumption in IT devices such as server. For example, the data center or the
like consumes 2000KW to cause the IT devices to operate at 1000KW, and PUE is 2.0.
By comparison, in the base station, the RUE is equal to or greater than 5 in terms of this
index. Thus, the base station is lower in energy efficiency.
[0022] As a cause for lowering the energy efficiency in the base station as described
above, there is a need for cooling equipment such as the AC 212. An ambient
temperature at which the BTS 211 is operative in the interior of the base station shelter
200 is, as described above, equal to or less than about 35 degrees C. This is because, a
power element (power-MOS-FET, or the like: member to be cooled ) incorporated into a
power amplifier section in the BTS 211 may possibly be damaged by heat if the
temperature exceeds 35 degrees C. Because of this, it is necessary to always control the
temperature in the interior of the base station shelter 200 to 35 degrees C or less by using
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the AC 212.
[0023] In the base station, the electric power consumption in the BTS 211 itself is 1KW
or less at maximum, while the electric power consumption in the AC 212 for performing
cooling to actuate the BTS 211 is about 4KW at maximum. That is, in the base station,
an amount of electric power consumed in the AC 212 for controlling the room
temperature to enable the BTS 211 to operate is greater than an amount of electric power
consumed by the operation of the BTS 211. For this reason, the amount of electric
power consumption in the base station depends on an outside air temperature which
directly affects the room temperature in the interior of the base station shelter 200, rather
than required electric power in the BTS 211.
[0024] In a configuration of, for example, the base station, in which the BTS
continuously consumes electric power and cooling heat consumption for temperature
control for the power element, etc., is necessary, cogeneration is efficiently used, which
uses an absorption chiller actuated by exhaust heat resulting from power generation.
However, the diesel engine (DE), a gasoline engine (GE), a micro gas turbine (MGT),
and the like, which are used as distributed power supply engines, as in the base station in
the present situation, etc., cannot become efficient cogeneration engines which supply
electric power to small-scale power consumption equipment. That is, an exhaust heat
temperature of at least about 200 degrees C is required to actuate the absorption chiller.
Regarding DE and GE, cooling water waste heat which occupies a most part of waste
heat has a temperature of about 90 degrees C, and is lower than the temperature required
to actuate the absorption chiller. In contrast, the MGT is able to attain exhaust heat of a
heat amount sufficient to actuate the absorption chiller, because its exhaust heat
temperature is about 250 degrees C. However, the MGT typically generates electric
power with 100KW or greater, in factories, or the like. It is difficult to reduce a size of
the MGT adaptively for generation of electric power with about several KW or less
which is necessary in the base station.
[0025] In addition, the electric power consumption in the base station depends on the
outside air temperature surrounding the base station shelter 200 as described above.
Because of this, a required cooling heat amount in the base station fluctuates depending
on season or time in one day. That is, a demand ratio between electricity and heat
(electricity-heat ratio) is varied depending on time or season. It is difficult to apply the
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conventional cogeneration in which a constant electricity-heat ratio is assumed.
[0026] In view of the above, a fuel cell having the following advantages is used as the
backup power supply for the base station. The fuel cell has advantages that its power
generation efficiency does not depend on a scale of electric power consumption facility,
unlike heat engines such as the above stated DE, GE or MGT, and the fuel cell is able to
supply electric power such that it flexibly addresses electric power consumption
fluctuating significantly. In addition, the fuel cell has advantages that it is able to
continue to generate desired electric power without stopping power generation due to
changes in natural environment, etc., unlike natural energy such as solar light power
generation.
[0027] In order to implement cogeneration with improved energy efficiency in which
the absorption chiller is actuated by utilizing the exhaust gas, a high-temperature
operative fuel cell such as a solid oxide fuel cell (SOFC) or a molten carbonate fuel cell
(MCFC) is suitably used.
[0028] Based of the above stated findings, the present invention provides the following
aspects.
[0029] Accoridng to a first aspect of the present invention, a cogeneration system
comprises a high-temperature operative fuel cell configured to generate electric power
through a power generation reaction by using a fuel supplied to the fuel cell and air
supplied to the fuel cell; a reformer configured to generate a reformed gas which
becomes the fuel, through a reforming reaction between a raw material gas supplied to
the reformer and a steam supplied to the reformer, by utilizing power generation reaction
heat generated in the high-temperature operative fuel cell and combustion heat of
unconsumed fuel; a vaporizer configured to generate the steam to be added to the raw
material gas supplied to the reformer by utilizing the power generation reaction heat and
the combustion heat; a cooling apparatus configured to cool a target by consuming a
portion of the power generation reaction heat and a portion of heat of an exhaust gas
having the combustion heat which remain after the reformer and the vaporizer have
consumed the heat, and cool the exhaust gas by consuming the portion of the heat; and a
condensation unit configured to cool the exhaust gas after the cooling apparatus has
consumed the portion of the heat owned by the exhaust gas to condense a moisture
contained in the exhaust gas to generate condensed water.
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[0030] The term “high-temperature operative fuel cell” refers to a fuel cell which is
operative at a temperature of 400 degrees C or higher. As the high-temperature
operative fuel cell, there are, for exmaple, a solid oxide fuel cell (SOFC), a molten
carbonate fuel cell (MCFC), and the like.
[0031] In accordance with the above described configuration, since the cogeneration
system includes the vaporizer, the reformer, and the high-temperature operative fuel cell,
the electric power is generated in power generation using the supplied air and the
reformed gas (fuel) generated from the raw material gas, and the electric power is
provided. The cooling apparatus is able to suitably cool the target such as components,
substances, or spaces which require cooling. That is, it is possible to practice the
cogeneration with improved energy efficiency, in which the cooling appartaus is actuated
by consuming a portion of the heat owned by the exhaust gas generated during the power
generation in the high-temperature operative fuel cell. Furthermore, the exhaust gas can
be cooled by consuming a portion of the heat owned by the exhaust gas when the cooling
apparatus is actuated.
[0032] The condensation unit is able to cool the exhaust gas after the cooling apparatus
has cooled the exhaust gas by consuming a portion of the heat owned by the exhaust gas
to condense the moisture contained in the exhaust gas to generate the condensed water.
Thus, in the cogeneration system according to the first aspect of the present invention,
the water required during the power generation in the high-temperature operative fuel
cell can be covered by recovering the moisture generated within the system.
[0033] Therefore, the cogeneration system according to the first aspect of the present
invention is able to achieve an advantage that the water can be supplied in a
self-sustaning manner within the eystem.
[0034] Accoridng to a second aspect of the present invention, in the cogeneratin system
according to the first aspect, the condensation unit may include a first heat exchanger
configured to heat the raw material gas to be supplied to the vaporizer by utilizing heat of
the exhaust gas after the cooling apparatus has consumed the portion of the heat; and a
second heat exchanger configured to heat the air to be supplied to the solid oxide fuel
cell by utilizing the heat of the exhaust gas after the first heat exchanger has utilized the
heat and to condense the moisture contained in the exhaust gas to generate the condensed
water.
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[0035] In accordance with the above described configuration, since the condensation
unit includes the first heat exchanger and the second heat exchanger, the raw material gas
and the air can be heated by utilizing the heat owned by the exhaust gas.
[0036] Thus, the heated air can be supplied to the high-temperature operative fuel cell
and the heated raw material gas can be supplied to the vaporizer. Therefore, a heat
energy required to raise the temperature of the air and a heat energy required when the
water is added to the raw material gas can be suppressed, and as a result, the temperature
of the heat owned by the exhaust gas can be raised. Thereby, energy (exergy) which can
be taken out of the exhaust gas can be increased.
[0037] The cooler performs the cooling, the first heat exchanger heats the raw material
gas, and the second heat exchanger heats the air, by utilizing the heat owned by the
exhaust gas. In this way, the heat owned by the exhaust gas can be consumed, and
finally, the temperature of the exhaust gas can be lowered to a temperature (e.g., about 40
degrees C) at which the water with an amount required for the power generation in the
high-temperature operative fuel cell is attained. Thus, the the cogeneration system
according to the second aspect of the present invention is able to cover the water required
for the power generation in the high-temperature operative fuel cell by recovering the
water generated within the system.
[0038] Accoridng to a third aspect of the present invention, in the cogeneratin system
according to the second aspect, the first heat exchanger may be a total enthalpy heat
exchanger which heats the raw material gas to be supplied to the vaporizer by utilizing
the heat of the exhaust gas after the cooling apparatus has consumed a portion of the heat
and humidifies the raw material gas by the moisture contained in the exhaust gas.
[0039] When the first heat exchanger is the total enthalpy heat exchanger, the raw
material gas can be heated and humidified by utilizing the heat owned by the exhaust gas.
[0040] Because of the above, the raw material gas heated and humidified can be
supplied to the vaporizer. Therefore, a heat energy required when the water is added to
the raw material gas can be suppressed, and as a result, the temperature of the heat owned
by the exhaust gas can be raised. Thereby, energy (exergy) which can be taken out of
the exhaust gas can be increased.
[0041] Accoridng to a fourth aspect of the present invention, in the cogeneratin system
according to the first aspect, the condensation unit may include a blower for air-cooling
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the exhaust gas after the cooling apparatus has consumed a portion of the heat; and the
blower may cool the exhaust gas to condensate the moisture contained in the exhaust gas
to generate the condensed water.
[0042] In accordance with this configuration, the blower is able to lower the
temperature of the exhaust gas to a temperature (e.g., about 40 degrees C) at which the
water of an amount required for the power generation in the high-temperature operative
fuel cell is attained.
[0043] Thus, the cogeneration system of the present invention is able to cover the water
required during the power generation in the high-temperature operative fuel cell by
recovering the moisture generated within the system.
[0044] Accoridng to a fifth aspect of the present invention, in the cogeneratin system
according to any one of the first to fourth aspects, the vaporizer may be configured to
vaporize the condensed water by utilizing the power generation reaction heat and the
combustion heat to generate the steam.
[0045] Accoridng to a sixth aspect of the present invention, in the cogeneratin system
according to any one of the first to fifth aspects, the cooling apparatus may be an
absorption cooling apparatus which causes a cooling medium to be absorbed into an
absorbing liquid and circulates the absorbing liquid; the cooling medium may have a
lower boiling temperature than the absorbing liquid; and the cogeneration system may
comprise a third heat exchanger configured to exchange heat between the exhaust gas
and the absorbing liquid containing the cooling medium to separate the cooling medium
from the absorbing liquid containing the cooling medium; and the absorbing liquid
containing the cooling medium may be vaporized by heat attained by the heat exchange
performed by the third heat exchanger.
[0046] Accoridng to a seventh aspect of the present invention, in the cogeneratin
system according to the sixth aspect, the absorption cooling apparatus may include: a
rectification device configured to liquefy only the absorbing liquid from the absorbing
liquid having been vaporized and containing the cooling medium, to separate the
absorbing liquid from the cooling medium; and a fourth heat exchanger configured to
exchange heat between vaporized cooling medium which has been separated from the
absorbing liquid by the rectification device and the air to be supplied to the solid oxide
fuel cell to liquefy the vaporized cooling medium; the air heated by the heat exchange
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with the vaporized cooling medium which is performed by the fourth heat exchanger may
be supplied to the high-temperature operative fuel cell.
[0047] In accordance with this configuration, since the absorption cooling apparatus
includes the fourth heat exchanger, it cools and liquefies the cooling medium vaporized
in the absorption cooling appartaus, and preliminarily heats the air supplied to the
high-temperature operative fuel cell.
[0048] Therefore, the absorption chiller can be operated stably, and the temperature of
the exhaust gas discharged from the high-temperature operative fuel cell can be improved.
Thereby, energy (exergy) which can be taken out of the exhaust gas can be increased.
[0049] Accoridng to an eighth aspect of the present invention, the the cogeneratin
system according to the third aspect may further comprise a water transporting unit
configured to transport the condensed water generated from the exhaust gas by the
second heat exchanger, to the first heat exchanger; and the condensed water transported
by the water transporting unit may be mixed with the exhaust gas to generate the exhaust
gas containing the condensed water as the steam; and the first heat exchanger may cause
the steam contained in the exhaust gas to be transferred to the raw material gas to heat
and humidify the raw material gas.
[0050] In accordance with this configuration, the water transporting unit is able to
transport the condensed water generated from the exhaust gas to the first heat exchanger.
The condensed water transported to the first heat exchanger is vaporized by the
high-temperature exhaust gas, and flows through the first heat exchange in a state in
which the steam is contained in the exhaust gas. That is, the exhaust gas containing
plenty of steam can heat and humidify the raw material gas in the first heat exchanger.
This enables the first heat exchanger to efficiently humidify the raw material gas
supplied to the high-temperature operative fuel cell.
[0051] Accoridng to a ninth aspect of the present invention, the cogeneratin system
accoridng to the eighth aspect, may further comprise a reduction reaction section
configured to reduce a sulfur compound contained in the raw material gas from a mixture
gas containing a portion of the reformed gas generated by the reformer and the raw
material gas, to generate hydrogen sulfide; and an adsorption section which adsorbs and
removes the hydrogen sulfide generated by the reduction reaction section; and the
reduction reaction section may be supplied with the exhaust gas to be supplied to the
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cooling apparatus, and a reaction temperature in the reduction reaction section is
maintained by the heat transferred from the exhaust gas.
[0052] Accoridng to a tenth aspect of the present invention, the cogeneratin system
according to any one of the first to ninth aspects, may further comprise a storage device
configured to store the electric power generated in the high-temperature operative fuel
cell.
[0053] Accoridng to an eleventh aspect of the present invention, the cogeneratin
system according to any one of the first to tenth aspects, the cooling apparatus may cool
at least a component which requires cooling as the target, in equipment actuated by the
electric power generated in the high-temperature operative fuel cell.
[0054] In accordance with this configuration, the equipment can be actuated by the
electric power generated in the high-temperature operative fuel cell, and the cooling
apparatus can be actuated by the exhaust gas generated during the power generation in
the high-temperature operative fuel cell, to cool the component which requires cooling in
the equipment. Therefore, it is possible to practice the cogeneration with improved
energy efficiency, in which the cooler is actuated by the exhaust gas generated during the
power generation in the high-temperature operative fuel cell.
[0055] Accoridng to a twelfth aspect of the present invention, in the cogeneratin system
according to the eleventh aspect, an upper limit value of a temperature to which the
component which requires cooling is cooled may be predetermined; and the cooling
apparatus may cool the component which requires cooling to a temperature lower than
the predetermined upper limit value.
[0056] Accoridng to a thirteenth aspect of the present invention, in the cogeneratin
system according to the eleventh or twelfth aspect, an amount of power generation in the
high-temperature operative fuel cell may be controlled based on temperature information
of the component which requires cooling.
[0057] In accordance with this configuration, the amount of power generation in the
high-temperature operative fuel cell can be controlled based on temperature information
of the component which requires cooling. For example, the operation and the amount
of power generation in the high-temperature operative fuel cell can be controlled
according to a demand of heat so that the temperature of the component which requires
cooling is kept at a temperature which is equal to or lower than a particular temperature.
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Since the operation and the amount of power generation in the high-temperature
operative fuel cell can be controlled by simple control in a heat-superior and
power-subordinate relationship, reliability of the system can be improved.
[0058] Accoridng to a fourteenth aspect of the present invention, in the cogeneratin
system according to one of the first to tenth aspects, the cooling apparatus may cool the
exhaust gas having been cooled by the condensation unit, as the target, to condense the
moisture contained in the exhaust gas to generate the condensed water.
[0059] In accordance with this configuration, the cooling appartaus is able to cool the
exhaust gas having been cooled by the condensation unit. The moisture contained in
the exhaust gas can be condensed to generate the condensed water. Thus, the
cogeneration system is able to increase an amount of generation of the condensed water
from the exhaust gas.
[0060] (Embodiment 1)
Hereinafter, preferred embodiment (Embodiment 1) of the present invention will
be described with reference to the drawings. Hereinafter, throughout the drawings, the
same or corresponding components are identified by the same reference symbols, and
will not be described in repetition.
[0061] (Cogeneration system)
Now, a description will be given of an example of a cogeneration system 100
implemented in the base station according to the present embodiment (Embodiment 1)
with reference to Fig. 1. Fig. 1 is a schematic view showing an exemplary
configuration of the cogeneration system 100 in the base station according to
Embodiment 1.
[0062] The cogeneration system 100 according to Embodiment 1 mainly comprises a
SOFC system (high-temperature operative fuel cell system) 101 which serves as a power
generating apparatus, a BTS (equipment) 11 within the base station shelter which utilizes
the electric power generated in the SOFC system 101, and an ammonia absorption chiller
(cooling appartaus, absorption cooling appartaus) for cooling a power element of a power
amplifier section in the BTS 11.
[0063] Further, the cogeneration system 100 comprises a power management system
(PMS)12 including a storage battery (SB 19) for backup and a diesel engine (DG) (not
shown) as an auxiliary power supply. The BTS 11 is supplied with the electric power
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from the SOFC system 101. The BTS 11 is configured to be supplied with electric
power from the SB 19 or from the DG via the PMS 12 when electric power is not
supplied from the SOFC system 101 to the BTS 11 or the electric power from the SOFC
system 101 is deficient.
[0064] That is, in the present embodiment, the base station is located in a region where
GID is not installed yet, and is configured such that the SOFC system 101 supplies the
electric power to the BTS 11 instead of supplying the electric power from the GRID to
the BTS 11. Also, the base station is located in a region where a water source such as
water for industrial use is not obtained, and is configured such that the SOFC system 101
recovers water from the exhaust gas and supplies the water to a vaporizer 15 in a SOFC
hot module 1 to be used for actuating the SOFC hot module 1.
[0065] The ammonia absorption chiller 10 is configured such that a regenerative heat
exchanger (third heat exchanger) 51 is heated by heat of the exhaust gas discharged from
the SOFC hot module 1 in the SOFC system 101, and an ammonia water solution is
vaporized by the heated regenerative heat exchanger 51 as a heat source, although its
detail will be described later.
[0066] As described above, the cogeneration system 100 according to Embodiment 1
comprises the ammonia absorption chiller 10 as a heat load, the BTS 11 as a power load
and the SOFC system 101 as the power generating apparatus. Power generation control
in a SOFC cell (high-temperature operative fuel cell) 13 in the SOFC system 101 is
performed according to the electric power consumption relating to communication in the
base station.
[0067] (Configuration of SOFC system)
The SOFC system 101 included in the cogeneration system 100 according to
Embodiment 1 will now be described. The SOFC system 101 is a power generation
system utilizing a SOFC (solid oxide fuel cell) as the fuel cell. As shown in Fig. 1, the
SOFC system 101 includes the SOFC hot module 1, a drain tank 2, a fuel processor
system (FPS) 3, a condensation unit 30, a blower 9, and a first condensed water pump 20.
[0068] The SOFC hot module 1 serves as a power generation apparatus in the
cogeneration system 100, and includes a SOFC cell 13 containing an anode 22 and a
cathode 23 therein, a combustion section 14, a vaporizer 15 and a reformer 16.
[0069] The SOFC cell 13 is a power generating section, and is provided with a current
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collecting member 17. Although not shown in Fig. 1, the SOFC cell 13 is electrically
connected to the BTS 11 as the power load via the current collecting member 17 and a
power converter (not shown).
[0070] The reformer 16 is configured to perform steam-reforming of a fuel (raw
material) gas such as a city gas. The vaporizer 15 vaporizes water used for the
steam-reforming, add steam to a fuel gas, and supplies the resulting fuel gas to the
reformer 16. The combustion section 14 is provided between the SOFC cell 13 and, the
reformer 16 and the vaporizer 15. Heat generated in the combustion section 14 covers
reforming reaction heat (reforming reaction energy) required in the reformer 16 and
vaporization heat (water vaporization energy) required in the vaporizer 15.
[0071] In the SOFC system 101, a regenerative heat exchanger 51 of the ammonia
absorption chiller 10 is configured to exchange heat between the exhaust gas discharged
from the SOFC hot module 1 and a cooling medium (ammonia). Specifically, the
ammonia absorption chiller 10 cools a target (power element of the power amplifier
section in the BTS 11) by consuming a portion of the heat owned by the exhaust gas, and
cools the exhaust gas discharged from the SOFC hot module 1 by consuming the portion
of the heat
[0072] Thereafter, the SOFC system 101 further cools the exhaust gas after the heat has
been consumed by the above stated heat exchange, to condense the moisture from the
exhaust gas. More specifically, in the SOFC system 101 of Embodiment 1, the
condensation unit 30 causes the exhaust gas after the heat has been consumed by the
above stated heat exchange, to radiate heat and lower its temperature to a level at which
the moisture can be condensed from the exhaust gas. Thus, in the SOFC system 101,
the water can be recovered from the exhaust gas.
[0073] Hereinafter, the condensation unit 30 in the SOFC system 101 according to
Embodiment 1 will be described more specifically.
[0074] (Condensation unit)
An exemplary configuration of the condensation unit 30 in the SOFC system
101 will be described with reference to Fig. 2. Fig. 2 is a schematic view showing an
exemplary configuration of the cogeneration system 100 in the base station according to
Embodiment 1.
[0075] As shown in Fig. 2, the condensation unit 30 includes a blower fan (blower) 31
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actuated by a motor and a radiator 32 through which the exhaust gas flows, to radiate
heat from the exhaust gas so that its temperature is lowered to a level at which the
moisture can be condensed from the exhaust gas. The blower fan 31 air-cools the
exhaust gas flowing through the radiator 32.
[0076] Since the condensation unit 30 is configured as described above, the
temperature of the exhaust gas can be lowered to a level at which the moisture can be
condensed from the exhaust gas. Thus, the water can be recovered from the exhaust
gas.
[0077] The condensation unit 30 may be configured in such a manner that a heat
exchanger exchanges heat between the supplied fuel (raw material) gas and the exhaust
gas to lower the temperature of the exhaust gas more efficiently as well as cooling of the
exhaust gas by the blower fan 31. Specifically, as shown in Fig. 3, the condensation
unit 30 further includes a total enthalpy heat exchanger 7 as a heat exchanger for
exchanging heat between the fuel (raw material) gas and the exhaust gas. Fig. 3 is a
schematic view showing an exemplary configuration of the cogeneration system 100 in
the base station according to Embodiment 1.
[0078] The exhaust gas having gone through the heat exchange in the regenerative heat
exchanger 51 of the ammonia absorption chiller 10 flows into the total enthalpy heat
exchanger 7, while the fuel (raw material) gas supplied to the SOFC hot module 1 also
flows into the total enthalpy heat exchanger 7. In the total enthalpy heat exchanger 7,
total enthalpy heat exchange occurs between the exhaust gas and the fuel (raw material)
gas. In the SOFC system 101, the blower fan 31 cools the exhaust gas having gone
through the total enthalpy heat exchange, thereby recovering the water from the exhaust
gas.
[0079] As defined herein, the heat exchange means that only heat is exchanged without
migration of substances, while the total enthalpy heat exchange means that heat exchange
occurs while the substances are migrating.
[0080] As described above, in the condensation unit 30, the total enthalpy heat
exchanger 7 performs the total enthalpy heat exchange between the exhaust gas and the
fuel (raw material) gas and the blower fan 31 cools the exhaust gas, thereby lowering the
exhaust gas efficiently.
[0081] In the total enthalpy heat exchanger 7, the heat owned by the exhaust gas and
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the moisture contained in the exhaust gas are transferred to the fuel (raw material) gas,
and thereby the fuel (raw material) gas is heated and humidified. Since the fuel (raw
material) gas can be heated preliminarily, the temperature of the exhaust gas discharged
from the SOFC hot module 1 can be raised. In addition, since the fuel (raw material)
gas can be humidified, the amount of reforming water supplied to the reformer 16 can be
reduced.
[0082] To raise the temperature of the exhaust gas discharged from the SOFC hot
module 1, as shown in Fig. 4, the condensation unit 30 may include a condensation heat
exchanger 8 instead of the blower fan 31 in the configuration of Fig. 3. Fig. 4 is a
schematic view showing an exemplary configuration of the cogeneration system 100 in
the base station according to Embodiment 1.
[0083] In the condensation unit 30, the total enthalpy heat exchanger 7 performs total
enthalpy heat exchange between the fuel (raw material) gas and the exhaust gas. Then,
the condensation heat exchanger 8 exchanges heat between the exhaust gas having gone
through the total enthalpy heat exchange and the air supplied to the SOFC hot module 1.
[0084] In the SOFC system 101 configured as described above, the temperature of the
exhaust gas can be lowered to a level at which the moisture can be condensed from the
exhaust gas in the cogeneration system 100. Thus, the water can be recovered from the
exhaust gas. Further, since the fuel (raw material) gas and the air can be supplied to the
SOFC hot module 1 after they are heated preliminarily, the temperature of the exhaust
gas discharged from the SOFC hot module 1 can be raised.
[0085] As shown in Fig. 4, the total enthalpy heat exchanger 7 includes a fuel passage
section 72 through which the fuel (raw material) gas flows and a heating section 71
through which the exhaust gas flows. The heating section 71 and the fuel passage
section 72 are separated from each other by a selective permeable membrane 73 which
allows selective permeation of a moisture. The total enthalpy heat exchanger 7
performs total enthalpy heat exchange between the steam contained in the exhaust gas
flowing through the heating section 71 and the fuel gas flowing through the fuel passage
section 72 (performs heat exchange while the substances are migrating) via the selective
permeable membrane 73. In this way, the fuel (raw material) gas is heated and
humidified.
[0086] As described above, the condensation unit 30 includes the total enthalpy heat
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exchanger 7 which performs total enthalpy heat exchange between the exhaust gas and
the fuel (raw material) gas. However, it is sufficient that the heat is transferred from the
exhaust gas to the fuel (raw material) gas, in order to lower the temperature of the
exhaust gas to generate condensed water. Therefore, instead of the total enthalpy heat
exchanger 7, a heat exchanger which exchanges heat between the exhaust gas and the
fuel (raw material) may be used. Nonetheless, the total enthalpy heat exchanger 7 is
suitably used, because it is able to heat and humidify the fuel (raw material) gas.
[0087] (Explanation of operation of SOFC System )
Next, by way of example, a basic operation of the SOFC system 101 having the
configuration of Fig. 4 will be described.
[0088] The SOFC hot module 1 is supplied with the fuel (raw material) gas and the air.
Before the fuel (raw material) gas is supplied to the SOFC hot module 1, the fuel
processor system (FPS) 3 removes impurities from the fuel (raw material) gas. Then,
the total enthalpy heat exchanger 7 heats and humidifies the fuel (raw material) gas by
the total enthalpy heat exchange with the exhaust gas discharged from the SOFC hot
module 1, and thereafter supplies the fuel (raw material) gas to the SOFC hot module 1.
[0089] The fuel (raw material) gas supplied to the SOFC hot module 1 is sent out to the
vaporizer 15. The vaporizer 15 adds the vaporized water to the fuel (raw material) gas,
and supplies a mixture gas of the fuel (raw material) gas and the steam, to the reformer
16.
[0090] During running of the SOFC system 101, air discharged from the cathode 23
and hydrogen discharged from the anode 22 are combusted in the combustion section 14.
The resulting combustion energy is utilized as vaporization heat (water vaporization
energy) consumed in the vaporizer 15, and as reforming reaction heat (reforming reaction
energy) consumed in the reformer 16. During start-up of the SOFC system 101, an
unreformed raw material is combusted in the combustion section 14, to preliminarily heat
an interior of the SOFC hot module 1.
[0091] A temperature of heat required in the reforming reaction in the reformer 16 is
about 650 degrees C. An amount of added water required for the reforming reaction is
such that S/C (steam carbon ratio: mol ratio between water and carbon in the raw
material) is equal to or more than 2.0 at least, and is typically about 2.5 to 3.0. The
SOFC hot module 1 is controlled so that these conditions are satisfied, and generates
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hydrogen-rich reformed gas from the raw material and the reforming water.
[0092] The reformed gas generated in the reformer 16 is supplied to the anode 22 of the
SOFC cell 13, while the air is supplied from the blower 9 to the cathode 23. An
electrochemical reaction proceeds as represented by the following formula:
H2 + 1/2O2 → H2O … (1)
This reaction is similar to a combustion reaction of hydrogen. A basic
principle of the fuel cell is such that energy equivalent to a combustion energy resulting
from this combustion reaction is taken out electrochemically. Through this reaction,
electric power is generated and heat is generated. The resulting heat (power generation
waste heat) resulting from the heat generation is utilized as a portion of the water
vaporization energy in the vaporizer 15 and a portion of the reforming reaction energy in
the reformer 16. In a case where the SOFC hot module 1 of Embodiment 1 is an
anode-supported SOFC, which is a recent main stream, its cell operation temperature is
about 700 degrees C.
[0093] As described above, in the SOFC hot module 1 in the SOFC system 101
according to Embodiment 1, the vaporizer 15 and the reformer 16 are actuated by
utilizing the waste heat resulting from the power generation in the SOFC cell 13 and
combustion heat of the surplus reformed gas. The SOFC cell 13 is actuated by the
reformed gas generated by the actuated vaporizer 15 and the actuated reformer 16. In
other words, in the SOFC hot module 1, a power regenerative mechanism is constructed.
[0094] The combustion exhaust gas discharged from the SOFC hot module 1 is a gas
obtained after the waste heat resulting from the power generation in the SOFC cell 13
and combustion heat of the surplus reformed gas have been utilized to actuate the
vaporizer 15 and the reformer 16, and contains water generated in the fuel cell and water
generated in the combustion, in the form of steam. A temperature of the exhaust gas is
about 250 degrees C. Because of this, this exhaust gas is utilized in heating for the
ammonia absorption chiller 10.
[0095] (Raw material (fuel) gas)
A raw material (fuel) gas supplied to the above stated SOFC system 101 will
now be described. Typically, as the raw material (fuel) gas, LNG (liquefied natural gas)
or LPG (liquefied petroleum gas) is used. Since impurities are removed automatically
from these gases when these gases are liquefied, these gases become high in purity.
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In view of safety, these gases are added with a certain amount of an odrant and supplied.
As the odrant, a sulfur compound is mainly used. However, the sulfur poisons a large
portion of catalysts. In some districts, a natural gas is supplied from a gas field to the
SOFC system 101 as the raw material (fuel) gas via a pipe line. In this case, the gas
contains a certain amount of sulfur in addition to hydrocarbon. In addition, in a case
where a nitrified gas (bio gas) is utilized as the raw material (fuel) gas, the nitrified gas
contains various odiferous substances.
[0096] To prevent the catalysts from being poisoned, by, for example, the odiferous
substances such as the sulfur contained in the raw material (fuel) gas as described above,
it is necessary to remove the odiferous substances from the raw material (fuel) gas as
much as possible before the raw material (fuel) gas is supplied to the reformer 16. To
this end, the SOFC system 101 of Embodiment 1 includes the fuel processor system
(FPS) 3 to remove the impurities. Note that the SOFC is high in operating temperature
differently from the PEFC. Because of this, the SOFC has an advantage that it is higher
in chemical resistance than the PEFC regarding an adsorbing/removing property of the
impurities with respect to the catalysts. Furthermore, since the SOFC is an anion type
(anions are supplied from the cathode to the anode, and react in the anode), most of
low-molecular volatile impurities are combusted in the anode.
[0097] The fuel processor system (FPS) 3 includes filters for removing the impurities
by water washing, adsorption, etc., to purify the raw material (fuel) gas. In particular, a
desulfurization filter within the fuel processor system 3 performs desulfurization. If the
raw material (fuel) gas contains a little sulfur compound, the fuel processor system (FPS)
3 may be omitted.
[0098] (Ammonia absorption chiller)
Next, a configuration of the ammonia absorption chiller 10 included as the heat
load in the cogeneration system 100 according to Embodiment 1 will be described. As
shown in Fig. 4, the ammonia absorption chiller 10 includes the regenerative heat
exchanger 51, a rectification device 62, a radiator 54, an absorption device 56, and a
storage container 57. As an absorbing liquid, water is used, while as a cooling medium,
ammonia is used. That is, the ammonia absorption chiller 10 uses as a working fluid a
mixture medium of the ammonia and the water.
[0099] An ammonia aqueous solution stored in the storage container 57 is heated and
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vaporized by a heat source in the regenerative heat exchanger 51. A mixture gas of the
water and the ammonia is divided in the rectification device 52. The water with a high
boiling point is returned to the storage container 57 and the absorption device 56 via the
regenerative heat exchanger 51, while only the ammonia with a low boiling point is
supplied to the radiator 54 through the rectification device 52.
[0100] The radiator 54 operates to cool and liquefy an ammonia vapor. Liquid
ammonia generated by cooling the ammonia vapor in the radiator 54 to cause the
ammonia vapor to radiate heat is supplied to a cooler 55 through a narrow tube. The
liquid ammonia having a higher concentration inside of the cooler 55 is vaporized and
absorbed into the water inside of the absorption device 56. The target (BTS 11) is
cooled in such a manner that the liquid ammonia deprives vaporization latent heat from
the target when the liquid ammonia is absorped into the water inside of the absorption
device 56. By executing this cycle continuously, the ammonia absorption chiller 10 can
lower the temperature of the heat of the exhaust gas supplied to the regenerative heat
exchanger 51 and take out cooling heat output from the ammonia absorption chiller 10.
[0101] More specifically, a COP of the ammonia absorption chiller 10 is 0.5 to 0.6.
The ammonia absorption chiller 10 is able to output cooling heat of 0.5 to 0.6 with
respect to the input heat 1.0. In addition, the ammonia absorption chiller 10 is able to
take out cooling heat output which is substantially proportional to the input heat energy.
A vapor generation temperature in a generating apparatus (not shown) in the ammonia
absorption chiller 10 is about 100 degrees C to 160 degrees C. Since the temperature of
the exhaust gas discharged from the SOFC hot module 1 is about 250 degrees C, the
ammonia absorption chiller 10 can be actuated.
[0102] As the vapor generation temperature is higher, a cooling attainment temperature
is lower. Therefore, in the case where a flow rate of the exhaust gas discharged from
the SOFC hot module 1 is equal, the cooling heat output increases as the temperature of
the exhaust gas increases. As the temperature of the exhaust gas is higher, the cooling
heat output from the ammonia absorption chiller 10 increases. Therefore, the apparatus
can be reduced in size, by reducing a heat exchange area of the regenerative heat
exchanger 51.
[0103] In view of the above stated advantages, the temperature of the exhaust gas input
to the regenerative heat exchanger 51 is suitably higher.
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[0104] (Configuration of BTS)
Next, the BTS 11 included as the power load in the cogeneration system 100
according to Embodiment 1 will be described.
[0105] Electric power consumption in the BTS 11 is about 800W under a maximum
load. The detail of 800W is such that electric power consumption in a control amplifier
section (not shown) which performs signal processing is 300W, electric power
consumption in the power amplifier section (not shown) which amplifies this signal and
converts it into an electric wave is 300W, and electric power consumption in an auxiliary
driving source such as an air-cooling fan (not shown) is 200W.
[0106] An amplification efficiency in the power amplifier section is improved year by
year. These days, the amplification efficiency is generally about 40%. The fact that
the power amplification efficiency is 40% means that the electric power of 100W is
needed to output a power amplification signal of 40W. The remaining 60W corresponds
to generated heat. That is, the heat generated in the power element in the power
amplifier section increases as the consumed energy (communication energy) relating to
the communication increases. In other words, this power element ambient temperature
T depends greatly on a magnitude of the communication energy.
[0107] A heat resistance temperature of general electronic components is about 70
degrees C to 80 degrees C. The control amplifier section which consumes a little
electric power need not be basically cooled, or it is sufficient that the control amplifier
section is cooled by normal air-cooling using a fan irrespective of an outside air
temperature (even though the outside air temperature is, for example, 50 degrees C).
[0108] By comparison, the temperature of the power element (power-MOS-FET, etc.)
for use in the power amplifier section reaches 200 degrees C or higher due to the above
stated heat generation, unless it is cooled, and exceeds a junction heat resistance
temperature (170 degrees C in the case of a Si element), so that the power element will
be broken. Since the temperature of the power element resulting from the heat
generation is high, it is not possible to implement sufficient cooling by the above stated
air-cooling using the air-cooling fan.
[0109] Accordingly, in the cogeneration system 100 according to Embodiment 1, the
ammonia absorption chiller 10 is able to cool the BTS 11 such that its operating
temperature (power element ambient temperature T) is equal to or lower than 35 degrees
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C.
[0110] To enable the BTS 11 with maximum electric power consumption of 800W to
operate stably, a heat amount which must be forcibly removed is 60% of 300W, i.e., heat
amount corresponding to 180W. The configuration in which an entire of the interior of
the gas station shelter is cooled to 35 degrees C or lower is inefficient. Accordingly, in
the cogeneration system 100 according to Embodiment 1, the entire of the interior of the
base station shelter is not cooled but a portion (power element in the power amplifier
section) to be forcibly cooled is directly cooled. The power generation amount in the
SOFC system 101 is controlled so that the power element ambient temperature T
becomes equal to or lower than a predetermined temperature (35 degrees C or lower).
[0111] In the case where the portion to be forcibly cooled is directly cooled, a cooling
amount which is proportional to the communication energy is given, thereby enabling the
base station to operate stably irrespective of the outside air temperature.
[0112] In the cogeneration system 100 according to Embodiment 1, a generated
electricity-heat ratio is constant and a consumed electricity-heat ratio is constant
irrespective of the outside air temperature in the base station. A value of the
electricity-heat ratio is a numeric value derived by dividing the electric power consumed
or generated by the heat consumed or generated. For example, in the case of an
apparatus which consumes electric power of 1000W and consumes cooling heat of 500W,
the value of the consumed electricity-heat ratio is 2. Or, in the case of an apparatus
which consumes electric power of 1000W and consumes cooling heat of 200W, the value
of the consumed electricity-heat ratio is 5.
[0113] That is, as the heat amount consumed with respect to an equal electric power is
less, the value of the consumed electricity-heat ratio is greater. In the present
embodiment, the generated heat amount is defined as a heat amount which is the
temperature of the exhaust gas discharged from the SOFC hot module 1, i.e., after the
vaporizer 15 and the reformer 16 have utilized power generation reaction heat and
combustion heat of unused fuel. By comparison, the consumed heat amount is a heat
amount generated in the BTS 11 after consuming the electric power in the power
amplifier section.
[0114] In the cogeneration system 100 according to Embodiment 1, the power
generation in the SOFC cell 13 is controlled so that the value of generated
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electricity-heat ratio becomes constant irrespective of the outside air temperature.
[0115] More specifically, the cogeneration system 100 is configured such that the value
of the ratio between the electric power generated by the power generation in the SOFC
cell 13 and the heat amount generated in conjunction with this power generation (value
of generated electricity-heat ratio) is equal to or less than the value of the ratio between
the electric power consumed in the power amplifier section in the BTS 11 and the heat
amount generated in conjunction with this electric power consumption (value of
consumed electricity-heat ratio). By controlling the power generation amount in the
SOFC cell 13 according to the electric power consumption relating to the communication
in the base station, the base station can be actuated stably.
[0116] As a result, the cogeneration system 100 of the present embodiment can be used
as a fuel supply system for a base station provided in a region which is physically
isolated and cannot another additional (auxiliary) power source, and where a weather is
severe and an outside air temperature fluctuates with a passage of time, or from season to
season.
[0117] (Electric power consumption in BTS)
Next, the electric power consumption in the above stated BTS 11 will be
described. The electric power consumed in the BTS 11 depends on the communication
amount as described above. When the electric power consumption is 800W at
maximum, an average power output during use is about 400W. Therefore, it is not
necessary to make a design so that the maximum power output generated in the SOFC 13
becomes always 800W. For example, a design may be made so that the maximum
power output generated in the SOFC cell 13 is 500W which is a little higher than the
average power output, and the resulting surplus electric power is stored in the SB 19
during the average power output. In addition, during the average power output, the
temperature to which the power amplifier section is excessively cooled by the ammonia
absorption chiller 10 is set lower than 35 degrees C.
[0118] As described above, during the average power output, the surplus electric power
is stored, and the power amplifier section is cooled to a temperature lower than 35
degrees C. Thereby, when the maximum power output (800W) is demanded, this
demand is met by supplying the electric power generated in the power generation and the
stored electric power. Since the power amplifier section is excessively cooled in
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advance to the temperature lower than 35 degrees C, the heat generated when the BTS 11
is actuated with the maximum power output can be addressed by surplus cooling heat and
cooling heat obtained by cooling by the ammonia absorption chiller 10.
[0119] Therefore, it becomes possible to operate the SOFC cell 13 stably under a
constant load although it is difficult to start-up and shut-down the SOFC cell 13, to
decrease its power generation efficiency to a specified value or less in view of
self-sustainable supply of heat, and to change a load promptly in response to a
communication load of the BTS 11 fluctuating rapidly.
[0120] In the cogeneration system 100 according to Embodiment 1, the consumed
electricity-heat ratio is substantially constant and the generated electricity-heat ratio is
substantially constant. Because of this, instead of controlling the power generation in
the SOFC cell 13 according to the electric power consumption relating to the
communication in the base station, the power generation may be controlled according to
the cooling heat consumption in the power element of the power amplifier section. In
the case of the configuration in which the power generation is controlled by the cooling
heat consumption, the cogeneration system 100 can attain required electric power supply
by performing simple control in the heat-superior and power-subordinate relationship in
which operation and power generation are performed according to a demand of heat, for
example, a cooling medium bath temperature is kept to a specified temperature or less
(e.g., 70 degrees C or less). Thus, the cogeneration system 100 can be actuated
properly by the simple control in the heat-superior and power-subordinate relationship,
and reliability of the system can be improved.
[0121] (Control of generated electricity-heat ratio)
Next, control of the generated electricity-heat ratio in the cogeneration system
100 will be described, using the cogeneration system 100 of Fig. 4 as an example. As
described above, the value of the generated electricity-heat ratio in the BTS 11 is 800W
(generated electric power) : 180W (generated heat amount) during the maximum power
output, i.e., about 4. By providing a configuration for attaining cooling heat
corresponding to the heat amount of 180W in the generated electricity-heat ratio of 4,
demand and supply of electric power and cooling heat can be balanced in the
cogeneration system 100.
[0122] In a case where the cogeneration system 100 is configured such that the cooling
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heat of 300W is generated with respect to the electric power of 800W during the
maximum power output, surplus cooling heat of about 100W is provided. In this
configuration, the cogeneration system 100 excessively cools the power element.
However, such excess cooling does not cause any problem in the operation of the power
element. On the other hand, in the case where the value of the generated electricity-heat
ratio is 8, i.e., only the heat amount of 100W can be attained with respect to the
generated electric power of 800W, the power element will be broken due to insufficient
cooling ability, which is a problematic. Because of this, in the case where the power
generation efficiency is the same, the heat amount obtained by unit power generation is
suitably more, i.e., the generated electricity-heat ratio is suitably smaller.
[0124] As described above, the exhaust gas discharged from the SOFC hot module 1
contains the water generated through the SOFC cell reaction and the water generated by
the combustion. In the cogeneration system 100 according to Embodiment 1, after the
ammonia absorption chiller 10 which is a heat source has consumed specified heat
amount, the exhaust gas is supplied to the total enthalpy heat exchanger 7. The
temperature of the heat exchanger in the ammonia absorption chiller 10 is about 150
degrees C. The exhaust gas with a temperature of 150 degrees C is supplied to the total
enthalpy heat exchanger 7.
[0125] The total enthalpy heat exchanger 7 is supplied with the above stated exhaust
gas and the fuel gas to be sent out to the SOFC hot module 1. The total enthalpy heat
exchanger 7 transfers the steam contained in the exhaust gas supplied via the ammonia
absorption chiller 10 to the fuel (raw material) gas using the selective permeable
membrane 72 in the total enthalpy heat exchanger 7 (performs total enthalpy heat
exchange). Thus, the steam contained in the exhaust gas and the heat owned by the
steam are transferred to the fuel gas.
[0126] The fact that the steam contained in the exhaust gas and the heat owned by the
steam are transferred to the fuel (raw material) gas by the total enthalpy heat exchanger 7
is equivalent to the fact that a portion of the reforming reaction heat (reforming
vaporization energy) consumed in the reformer 16 is recovered from the exhaust gas.
Because of this, the reforming reaction heat (reforming vaporization energy) consumed
in the SOFC hot module 1 can be reduced while maintaining a fuel consumption ratio.
As a result, the temperature of the exhaust gas discharged from the SOFC hot module 1
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can be raised. Thereby, an amount of energy consumed to actuate the ammonia
absorption chiller 10 provided in a subsequent stage of the SOFC hot module 1 increases.
That is, the value of generated electricity-heat ratio can be reduced although the power
generation efficiency is constant. Transferring the steam contained in the exhaust gas to
the fuel gas means that the water is recovered and re-used. This can lead to
self-sustainable supply of water in the base station located in conditions of site in which
no water source is obtained.
[0127] The temperature of the exhaust gas cannot be lowered sufficiently to a level at
which the steam contained in the exhaust gas can be recovered as the condensed water,
when only the total enthalpy heat exchanger 7 is used. Accordingly, the cogeneration
system 100 of Embodiment 1 of Fig. 4 further includes the condensation heat exchanger
8 as described above. The exhaust gas which has gone through the total enthalpy heat
exchange in the total enthalpy heat exchanger 7 is supplied to the condensation heat
exchanger 8, and the air to be sent out the SOFC hot module 1 is supplied to the
condensation heat exchanger 8. The condensation heat exchanger 8 exchanges heat
between this air and the exhaust gas, thereby preliminarily heating the air to be sent out
the SOFC hot module 1.
[0128] The cogeneration system 100 of Embodiment 1 of Fig. 4 is able to send out the
preliminarily heated air to the SOFC hot module 1, and reduce the vaporization heat
consumed in the SOC hot module 1. This makes it possible to raise the temperature of
the exhaust gas discharged from the SOFC hot module 1.
[0129] The temperature of the exhaust gas can be lowered to a temperature at which the
condensed water can be generated, by the heat exchange with the air in the condensation
heat exchanger 8. The condensed water derived from the exhaust gas is stored in the
drain tank 2 as the reforming water. The condensed water stored in the drain tank 2 is
supplied to the vaporizer 15 within the SOFC hot module 1, by an operation of a first
condensed water pump 20.
[0130] In the above described manner, since the steam contained in the exhaust gas can
be stored in the drain tank 2 as the reforming water and the stored condensed water can
be supplied to the vaporizer 15, the self-sustainable supply of water can be achieved in
the base station located in conditions of site in which no water source is obtained. The
self-sustainable supply of water will be described later.
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[0131] The cogeneration system 100 of Embodiment 1 of Fig. 4 is configured to supply
electric power from auxiliary power sources (e.g., solar light power generation, wind
power power generation) other than the SOFC cell 13, to the power converter (not
shown).
[0132] For example, it is supposed that the cogeneration system 100 is configured to
perform control for cooling in the heat-superior and power-subordinate relationship,
instead of performing control for the power generation in the SOFC cell 13 according to
the electric power consumption relating to the communication. In this case, if the value
of generated electricity-heat ratio is smaller, the SOFC cell 13 cannot cover all of desired
electric power. In that case, it is desirable to supply the electric power from the
auxiliary power source in addition to the SOFC cell 13.
[0133] Regenerative energy of the exhaust gas, or the like supplied to the ammonia
absorption chiller 10 is not energy generated by consuming the fuel cell for the purpose
of attaining the regenerative energy. By managing power using the SOFC cell 13 as a
base load power supply and using the auxiliary power source together with the SOFC cell
13, fuel consumption can be reduced. The reduction of the fuel consumption provides
an advantage in management that a frequency with which a fuel tank is changed can be
reduced, for example.
[0134] Next, Modified examples (Modified example 1 to modified example 4) of the
above described cogeneration system 100 of Embodiment 1 of Fig. 4 will be described.
[0135] (Modified example 1)
As shown in Fig. 4, the ammonia absorption chiller 10 in the cogeneration
system 100 of Embodiment 1 is configured to cause the radiator 54 to cool the generated
cooling medium vapor (vaporized ammonia) for condensation and liquefaction.
Alternatively, as shown in Fig. 5, instead of the radiator 54, the ammonia absorption
chiller 10 may include a cooling medium condensation heat exchanger (fourth heat
exchanger) 58 which is supplied with the air to be sent out to the SOFC hot module 1 and
exchanges heat between this air and the cooling medium vapor. Fig. 5 is a schematic
view showing an exemplary configuration of a cogeneration system 100 according to
Modified example 1 of Embodiment 1. Since the cogeneration system 100 of Fig. 5 is
identical in configuration to the cogeneration system 100 of Fig. 4 except that the
radiator 54 is replaced by the cooling medium condensation heat exchanger 58, the
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components other than the cooling medium condensation heat exchanger 58 are
identified by the same reference symbols and will not be described in repetition.
[0136] In this configuration, the ammonia absorption chiller 10 is able to cool and
condense the cooling medium vapor and preliminarily heat the air to be sent out to the
SOFC hot module 1.
[0137] Thus, the ammonia absorption chiller 10 can operate stably and the temperature
of the exhaust gas discharged from the SOFC hot module 1 can be increased. In other
words, exergy of the exhaust gas can be improved. Although Modified example 1 has
been described as Modified example of the cogeneration system 100 having the
configuration of Fig. 4, it may be applicable to the cogeneration system 100 having the
configuration of Fig. 2 or Fig. 3. That is, in the cogeneration system 100 having the
configuration of Fig. 2 or Fig. 3, as shown in Fig. 5, instead of the radiator 54, the
ammonia absorption chiller 10 may include the cooling medium condensation heat
exchanger (fourth heat exchanger) 58 which is supplied with the air to be sent out to the
SOFC hot module 1 and exchanges heat between this air and the cooling medium vapor.
[0138] (Modified example 2)
In the cogeneration system 100 of Fig. 4, the total enthalpy heat exchanger 7 is
supplied with the fuel (raw material) gas and the exhaust gas. Alterantively, as shown
in Fig. 6, in Modified example 2, the cogeneration system 100 may further comprise a
second condensed water pump (water transporting unit) 21 which supplies the condensed
water from the drain tank 2 to the total enthalpy heat exchanger 7. Fig. 6 is a schematic
view showing an exemplary configuration of the cogeneration system 100 according to
Modified example 2 of Embodiment 1. Since the cogeneration system 100 of Fig. 6 is
identical in configuration to the cogeneration system 100 of Fig. 4 except that the water
can be supplied from the drain tank 2 to the total enthalpy heat exchanger 7, the same
components as those of the cogeneration system 100 of Fig. 4 are identified by the same
reference symbols, in the cogeneration system 100 of Modified example 2, and will not
be described in repetition.
[0139] The total enthalpy heat exchanger 7 supplied with the fuel gas, the exhaust gas
and the water from the drain tank 2 has, for example, a configuration of Fig. 7. Fig. 7 is
a schematic view showing an exemplary configuration of the total enthalpy heat
exchanger 7 in the cogeneration system 100 of Fig. 6.
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[0140] As shown in Fig. 7, the total enthalpy heat exchanger 7 includes a fuel passage
section 72 through which the fuel (raw material) gas flows and a heating section 71
through which the exhaust gas flows. In the total enthalpy heat exchanger 7, the heating
section 71 and the fuel passage section 72 are separated from each other by the selective
permeable membrane 73 which allows selective permeation of a moisture. In the total
enthalpy heat exchanger 7, the condensed water and the exhaust gas directly contact with
other and exchange heat between them (they are mixed) to generate the steam at one side
of the selective permeable membrane 73, i.e., the heating section 71. The total enthalpy
heat exchange between the generated steam and the fuel (raw material) gas flowing
through the fuel passage section 72 proceeds via the selective permeable membrane 73.
In this way, the fuel (raw material) gas is heated and humidified. The heat exchange
using the direct-contact heat exchange and the total enthalpy heat exchange has
advantages that the power efficiency is high and the device can be simplified and reduced
in size easily.
[0141] The temperature of the exhaust gas discharged from the ammonia absorption
chiller 10 is about 150 degrees C and this exhaust gas has an energy enough to vaporize
the supplied condensed water. In Modified example 2, the fuel gas can be further
humidified by supplying the condensed water stored in the drain tank 2 to the total
enthalpy heat exchanger 7.
[0142] The condensation heat exchanger 8 provided in a subsequent stage of the total
enthalpy heat exchanger 7 exchnages heat between the steam (condensed water) mixed
with the exhaust gas and the air. The condensed water is recovered and stored into the
drain tank 2.
[0143] (Modified example 3)
In the cogeneration system 100 according to Modified example 2, like Modified
example 1, the ammonia absorption chiller 10 may include the cooling medium
condensation heat exchanger 58 instead of the radiator 54.
[0144] (Modified example 4)
In Modified example 4, as shown in Fig. 8, the cogeneration system 100 may
further includes in the configuration of Modified example 3, a fuel check valve 4, a
reformed gas check valve 5, a hydrogenated desulfurization heat exchanger (reduction
reaction section) 6, and a trap (TRAP) (adsorbing section) 18. The hydrogenated
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desulfurization heat exchanger 6 performs desulfurization performed in the
desulfurization filter within the fuel processor system 3. Fig. 8 is a schematic view
showing an exemplary configuration of the cogeneration system 100 according to
Modified example 4 of Embodiment 1.
[0145] The cogeneration system 100 according to Modified example 4 is identical in
configuration to the cogeneration system of Modified example 3 except that the
cogeneration system 100 according to Modified example 4 further includes the fuel
check valve 4, the reformed gas check valve 5, the hydrogenated desulfurization heat
exchanger 6, and the trap (TRAP) 18. Therefore, the components other than the added
components will not be described in repetition.
[0146] The hydrogenated desulfurization heat exchanger 6 is able to remove a sulfur
compound from the fuel (raw material) gas, and exchange heat between the exhaust gas
flowing through an exhaust gas side passage of the hydrogenated desulfurization heat
exchanger 6 and the fuel gas flowing through a fuel gas side passage of the hydrogenated
desulfurization heat exchanger 6, thereby performing the desulfurization as described
below.
[0147] The hydrogenated desulfurization heat exchanger 6 performs reduction of the
sulfur compound contained in the fuel (raw material) gas, by using, for example, copper
zinc catalyst, to generate hydrogen sulfide. Then, the hydrogenated desulfurization heat
exchanger 6 removes the generated hydrogen sulfide by using an adsorption agent such
as an iron oxide.
[0148] An optimal temperature at which the fuel (raw material) gas is heated to allow
this reduction reaction to proceed is about 250 degrees C to 300 degrees C.
[0149] An internal temperature of the SOFC hot module 1 is about 650 degrees C to
700 degrees C. The temperature of the exhaust gas discharged from the SOFC hot
module 1 is about 250 degrees C. Therefore, the fuel (raw material) gas cannot be
heated up to the above stated optimal temperature.
[0150] On the other hand, in the cogeneration system 100, the condensation heat
exchanger 8 and cooling medium condensation heat exchanger 58 preliminarily heat the
air to be supplied to the SOFC hot module 1, and the total enthalpy heat exchanger 7
heats and humidifies the fuel (raw material) gas, so that the temperature of the exhaust
gas discharged from the SOFC hot module 1 can be made about 300 degrees C. Thus,
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the fuel can be heated up to the above stated optimal reaction temperature. Therefore,
hydrogenated desulfurization can be performed with a simple configuration.
[0151] In the cogeneration system 100 according to Modified example 4, the fuel check
valve 4 is provided in a passage between the fuel processor system 3 and the
hydrogenated desulfurization heat exchanger 6, and the reformed gas check valve 5 is
provided in a passage between the reformer 16 and the hydrogenated desulfurization heat
exchanger 6. The trap (TRAP) 18 is provided in a location downstream of the
hydrogenated desulfurization heat exchanger 6 and between the hydrogenated
desulfurization heat exchanger 6 and the total enthalpy heat exchanger 7.
[0152] A portion of the hydrogen-rich reformed gas generated in the reformer 16 is
drawn to outside of the SOFC hot module 1, and then mixed with the fuel (raw material)
gas via the reformed gas check valve 5. That is, a portion of the reformed gas to be
supplied to the SOFC cell 13 is divided to flow toward outside of the SOFC hot module 1
and mixed with the fuel (raw material) gas outside of the SOFC hot module 1. The fuel
check valve 4 is configured to prevent a back flow of the fuel (raw material) gas.
[0153] The mixture gas is supplied to hydrogenated desulfurization heat exchanger 6
and heated up to the above stated optimal temperature by the exhaust gas flowing
through the exhaust gas side passage of hydrogenated desulfurization heat exchanger 6.
After the sulfur compound is subjected to the reduction reaction in the above stated
catalyst, the mixture gas is discharged.
[0154] The trap (TRAP) 18 is provided in the location downstream of the hydrogenated
desulfurization heat exchanger 6. The trap (TRAP) 18 adsorbs the generated hydrogen
sulfide thereto. These members are located outside of the SOFC hot module 1 and
maintenance of these members, for example, change can be easily carried out. Since
the water impedes the reduction reaction, the reduction reaction is preferably performed
before the fuel is humidified as shown in Fig. 8.
[0155] A reduction catalyst (not shown) is provided in the fuel side passage of
hydrogenated desulfurization heat exchanger 6. In a case where a catalyst life is
reduced in a state in which the temperature is higher than, for example, 300 degrees C,
depending on the kind of a reduction reaction catalyst, the cooling medium condensation
heat exchanger 58 may be omitted, but instead the radiator 54 may be provided to
slightly lower the temperature of the combustion gas, off course, depending on its
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optimal temperature range.
[0156] The above stated plurality of heat exchangers can be combined suitably
depending on restrain conditions and use environment, etc.. For example, in a case
where a sulfur concentration is very small and already known, adsorption desulfurization
is more advantageous and the hydrogenated desulfurization heat exchanger 6 is
unnecessary. In other words, all of the plurality of heat exchangers need not be
provided.
[0157] In a case where it is necessary to further lower the temperature of the exhaust
gas to increase the amount of recovery of the condensed water and enhance a recovery
efficiency, the condensation heat exchanger 8 exchanges heat between the air and the
exhaust gas and then supplies the exhaust gas to the cooler 55, which may further cool
the exhaust gas. In such a configuration, the cooler 55 is required to attain a cooling
heat amount required to cool the exhaust gas to a predetermined temperature in addition
to at least a cooling heat amount required to cool the power amplifier section of the BTS
11. In recent BTS for base station, a power amplifier is provided with a heat pipe to
radiate heat to outside so that electric power for air conditioning equipment such as an air
conditioner in especially high-temperature region becomes unnecessary. In this case,
the power amplifier does not require the cooling heat. Therefore, it is sufficient that the
cooler 55 cools the exhaust gas to a predetermined temperature and covers a required
amount of cooling heat.
[0158] (Improvement of exergy and self-sustainable supply of water)
Next, a description will be given in more detail of an advantage that the
cogeneration system 100 can raise the temperature of the exhaust gas because of
provision of the heat exchangers such as the total enthalpy heat exchanger 7 and the
condensation heat exchanger 8 (improvement of exergy). Specifically, this will be
described in conjunction with the cogeneration system 100 of Fig. 4 as an example.
[0159] In addition, a description will be specifically given of an advantage that the
cogeneration system 100 can attain the required water in a course of a running of the base
station without being supplied with water from outside (self-sustainable supply of water).
[0160] As described above, the exhaust gas discharged from the SOFC hot module 1
contains as the steam the water generated through the cell reaction and the water
generated by the combustion. This steam is not condensed in a generated heat
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exchanger temperature (about 150 degrees C) in the ammonia absorption chiller 10, but
discharged from the ammonia absorption chiller 10 in the form of the steam. As
described above, this water is recovered and used to heat and humidify the fuel gas,
thereby reducing the reforming water supplied to the vaporizer 15.
[0161] Here it is assumed that in a normal operating condition in the SOFC hot module
1, a power generation efficiency is 1KW. In a case where the vaporizer 15 within the
SOFC hot module 1 supplies all of the reforming water used in the reformer 16, under
this condition, the temperature of the exhaust gas is about 250 degrees C. By
comparison, in a case where the fuel (raw material) gas is humidified by the steam
generated by vaporization in a vaporizer provided outside of the SOFC hot module 1
before it is supplied to the SOFC hot module 1, the temperature of the exhaust gas is
about 450 degrees C.
[0162] Therefore, in a case where the total enthalpy heat exchanger 7 heats and
humidifies a portion of the fuel (raw material) gas, like the cogeneration system 100
according to Embodiment 1 of Fig. 4, the temperature of the exhaust gas falls within a
range between 250 degrees C and 450 degrees C. That is, the temperature of the
exhaust gas rises and becomes higher than 250 degrees C.
[0163] Now, a description will be given of supply and generation of substances and the
attained temperature of the combustion gas in the SOFC hot module 1, in the
cogeneration system 100 according to Embodiment 1, with reference to Fig. 9. It is
assumed that the fuel gas supplied to the SOFC hot module 1 is a methane gas. Fig. 9 is
a view showing an example of supply and generation of substances in a reforming
efficiency and a fuel/oxygen use (utilization) efficiency, in a cell reaction in which water
of 1 mol is generated from hydrogen of 1 mole and oxygen of 0.5 mol in the
cogeneration system 100 according to Embodiment 1.
[0164] The fuel (raw material) gas and the air supplied to the SOFC hot module 1 are
converted finally into an exhaust gas having a composition of carbon diode, water,
nitrogen, and oxygen. A steam partial pressure in this case is about a dew point of 65
degrees C as represented by an exhaust gas composition of Fig. 9. The exhaust gas can
be humidified at a temperature of about a dew point of 60 degrees C through the total
enthalpy heat exchange (see fuel humidified state).
[0165] When a fuel use efficiency in the SOFC hot module 1 is 80%, a reforming
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efficiency is 80% and S/C is 2.5, reforming water of 0.98mol is needed as shown in Fig.
9.
[0166] In this system, as represented by the exhaust gas composition, water of 1.48mol
is generated in this system. In this case, a steam partial pressure in the combustion gas
composition is 24,996Pa, and its dew point is 65 degrees C. If the water of 0.98mol can
be recovered from the steam of 1.48mol in the exhaust gas composition, then
self-sustainable supply of water is achieved.
[0167] The total enthalpy heat exchanger 7 performs the total enthalpy heat exchange
to supply to the fuel (raw material) gas, water about 0.1mol corresponding to 10% of the
water 0.98mol which is necessary for the reforming. Due to saving of vaporization heat
of this, the temperature (waste heat temperature) of the exhaust gas is raised by 10% of
200 degrees C which is a difference between 450 degrees C and 250 degrees C, i.e.,
about 20 degrees C.
[0168] The exhaust gas of about 150 degrees C which is discharged from the ammonia
absorption chiller 10 has an energy for vaporizing the water with the above stated amount
or more. As described in Modified example 2 to Modified example 4, the condensed
water stored in the drain tank 2 is supplied to the total enthalpy heat exchanger 7, and
thereby the fuel (raw material) gas can be further humidified. Fig. 10 shows supply and
generation of the substances in the cogeneration system 100 and the attained temperature
of the combustion gas in the SOFC hot module 1, in this case. Fig. 10 is a view
showing an example of supply and generation of the substances in a reforming efficiency
and a fuel/oxygen use efficiency, in a cell reaction in which water of 1 mol is generated
from hydrogen of 1 mol and oxygen of 0.5 mol in the cogeneration system 100 according
to Embodiment 1.
[0169] As shown Fig. 10, the condensed water stored in the drain tank 2 is supplied to
the total enthalpy heat exchanger 7, which performs the total enthalpy heat exchange to
supply to the fuel (raw material) gas, water about 0.21mol. That is, this humidification
of the fuel (raw material) gas covers about 20% of the amount of the water required for
the reforming in the reformer 16, thereby resulting in a temperature of the exhaust gas
which is close to 300 degrees C.
[0170] As indicated by the fuel humidified state of Fig. 10, the dew point is
substantially equal to the temperature of the exhaust gas discharged from the total
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enthalpy heat exchanger 7. The condensation heat exchanger 8 exchanges heat between
this exhaust gas and the air supplied to the SOFC hot module 1, and supplies the
pre-heated air to inside of the SOFC hot module 1. This makes it possible to further
raise the temperature of the exhaust gas discharged from the SOFC hot module 1.
[0171] A temperature increase of the exhaust gas which is attained as described above
is about 20 degrees C in the case where attained air temperature is 70 degrees C (room
temperature + 50 degrees C). Therefore, by combining the total enthalpy heat exchange
performed by the total enthalpy heat exchanger 7 and the heat exchange performed by the
condensation heat exchanger 8 and by providing the cooling medium condensation heat
exchanger 58 like Modified example 1, the temperature of the exhaust gas discharged
from the SOFC hot module 1 exceeds 300 degrees C.
[0172] Therefore, in a case where the cogeneration system 100 has the configuration
according to Modified example 4, the hydrogenated desulfurization heat exchanger 6 can
heat the fuel gas up to the above stated optimal reaction temperature, and thus
hydrogenated desulfurization can be performed with a simple configuration. In addition,
since the temperature of the exhaust gas can be raised to become higher than 300 degrees
C, even the exhaust gas which has gone through the heat exchange in the hydrogenated
desulfurization heat exchanger 6 can keep exergy enough to actuate the ammonia
absorption chiller 10.
[0173] In the case where the condensed water is supplied from the drain tank 2 to the
total enthalpy heat exchanger 7 like the configuration of Modified example 2 to Modified
example 4, the condensation heat exchanger 8 can recover the condensed water
remaining after the total enthalpy heat exchanger 7 has heated and humidified the fuel
gas. Thus, the water required in the vaporizer 15 can be covered.
[0174] Now, conditions for achieving self-sustainable supply of water will be discussed
with reference to an example of the supply and generation of the substances in the
reforming efficiency and the fuel/oxygen use efficiency, in the cell reaction in which
water of 1 mol is generated from hydrogen of 1 mol and oxygen of 0.5 mol in the
cogeneration system 100, shown in Fig. 10.
[0175] As shown in Fig. 10, the reforming water required in the reforming reaction is
0.98mol. The steam in the exhaust gas composition is 1.48mol. Therefore, if the
water of 0.98mol, of the water of 1.48mol in the exhaust gas, can be recovered from the
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exhaust gas, this can cover the reforming water. That is, in this case, the water
discarded to outside the system must be equal to or less than(1.48mol – 0.98mol =
0.51mol).
[0176] In this case, the steam partial pressure must be equal to or less than 10209Pa as
described above. Since the water which has been recovered from a total mol number of
6.02mol of the discharged exhaust gas and flows toward the reformer 16 is 0.98mol, the
steam partial pressure output from the condensation heat exchanger 8 must be equal to or
less than 101300 (Pa: total pressure) * (0.51/ (6.02 - 0.51)) = 10209Pa. This is
converted into a dew point of 46 degrees C. Unless the exhaust gas is cooled to 46
degrees C or less, the water required to operate the base station is not attained. In other
words, the self-sustainable supply of water in the base station is not achieved.
[0177] In view of this, in the cogeneration system 100 according to Embodiment 1 of
Fig. 4, the exhaust gas is used to actuate the ammonia absorption chiller 10 in a first
stage as described above. Then, the total enthalpy heat exchanger 7 transfers rough heat
from the exhaust gas which has been used in the ammonia absorption chiller 10 and has
been lowered in temperature, to the fuel (raw material) gas. Finally, the condensation
heat exchanger 8 exchanges heat between the exhaust gas and the air, thus enabling the
exhaust gas to be finally lowered to a temperature at which self-sustainable supply of
water is achieved.
[0178] As described above, the cogeneration system 100 according to Embodiment 1 of
Fig. 4 includes the plurality of heat exchangers (total enthalpy heat exchanger 7,
condensation heat exchanger 8, and cooling medium condensation heat exchanger 58),
and can enhance the exergy of the exhaust gas.
[0179] In addition to the above stated plurality of heat exchangers, the cogeneration
system 100 includes the regenerative heat exchanger 51. The regenerative heat
exchanger 51 is heated by the exhaust gas to actuate the ammonia absorption chiller 10.
Also, in some cases, the cogeneration system 100 includes the hydrogenated
desulfurization heat exchanger 6, which is heated by the exhaust gas to remove the sulfur
compound from the fuel (raw material) gas. As a result, the exhaust gas can be finally
lowered to 46 degree C or less at which self-sustainable supply of water is achieved.
[0180] Therefore, in the cogeneration system 100, the SOFC system 101 serves as a
base power supply, and an overall efficiency can be enhanced and self-sustainable supply
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of water can be achieved, by cogeneration using the SOFC system 101 and the ammonia
absorption chiller 10. Because of this, even when the base station is located in a region
where there is no water source and the GRID is not installed, its management can be
made easier and a higher yieldability is attained.
[0181] (Embodiment 2)
In Embodiment 1, a description has been given of the cogeneration system 100
including the SOFC system 101 which serves as the power generating apparatus, the BTS
(equipment) 11 which is located within the base station shelter and utilizes the electric
power generated in the SOFC system 101, and the ammonia absorption chiller (cooling
apparatus, absorption cooling apparatus) 10 for cooling the power element of the power
amplifier section in the BTS 11.
[0182] In Embodiment 2, a description will be given of the cogeneration system 100 in
a case where cooling of the BTS 11 is unnecessary, with reference to Fig. 11. Fig. 11 is
a schematic view showing an exemplary configuration of the cogeneration system 100
according to another embodiment (Embodiment 2). In the SOFC system 101 according
to Embodiment 2, the condensation unit 30 is configured as the condensation unit 30 of
Fig. 4. However, the present invention is not limited to this. For example, the
condensation unit 30 in the SOFC system 101 according to Embodiment 2 may be
configured as shown in Figs. 1 to 3.
[0183] The cogeneration system 100 according to Embodiment 2 is configured in such
a manner that the ammonia absorption chiller 10 cools the exhaust gas to generate the
condensed water instead of cooling the power amplifier section of the BTS 11. That is,
a target cooled by the ammonia absorption chiller 10 is the exhaust gas, from which the
condensed water has been recovered by cooling in the condensation uni 30. In the
cogeneration system 100 according to Embodiment 2, the same components as those of
the cogeneration system 100 according to Embodiment 1 are identified by the same
reference symbols and will not be described in repetition.
[0184] The cogeneration system 100 according to Embodiment 2 is different from the
cogeneration system 100 according to Embodiment 1 (especially, Modified example 2 of
Fig. 6) in that the ammonia absorption chiller 10 cools the exhaust gas discharged from
the condensation heat exchanger 8 instead of cooling the BTS 11.
[0185] In the cogeneration system 100 according to Embodiment 2, like the
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cogeneration system 100 according to Embodiment 1, the heat owned by the exhaust gas
discharged from the SOFC hot module 1 is utilized to actuate the ammonia absorption
chiller 10. That is, the ammonia absorption chiller 10 consumes a portion of the heat
owned by the exhaust gas, thereby cooling the exhaust gas discharged from the SOFC hot
module 1. The total enthalpy heat exchanger 7 performs the total enthalpy heat
exchange between the exhaust gas from which a certain amount of heat has been
consumed and the fuel (raw material) gas to be supplied to the SOFC hot module 1.
Furthermore, the condensation heat exchanger 8 exchanges heat between the exhaust gas
after the total enthalpy heat exchange and the air to be supplied to the SOFC hot module
1. Through this heat exchange, the condensed water is generated from the exhaust gas,
and the generated condensed water is stored in the drain tank 2. Furthermore, to obtain
the condensed water from the exhaust gas, the exhaust gas which has gone through the
heat exchange in the condensation heat exchanger 8 is supplied to the cooling section 60
of the ammonia absorption chiller 10. The cooling section 60 further cools the exhaust
gas. Thus, the cogeneration system 100 according to Embodiment 2 is able to increase
an amount of the condensed water generated from the exhaust gas.
[0186] In the cogeneration system 100 according to Embodiment 2, an object which
consumes the electric power generated in the SOFC system 101 is not limited to the base
station (BTS 11 within the base station shelter), but may be a general power load 61 as
shown in Fig. 12. Fig. 12 is a schematic view showing an exemplary configuration of a
cogeneration system according to another embodiment (Embodiment 2).
[0187] Although in the present embodiment, the SOFC has been exemplarily described
as the power generating apparatus, the present invention is not limited to this. For
example, the power generating apparatus may be a molten carbonate fuel cell (MCFC).
That is, the power generating apparatus may be a high-temperature operative fuel cell
which is operative at a high temperature of, for example, 400 degrees C or higher and
attains a high-temperature exhaust gas.
[0188] Numeral modifications and alternative embodiments of the present invention
will be apparent to those skilled in the art in view of the foregoing description.
Accordingly, the description is to be construed as illustrative only, and is provided for the
purpose of teaching those skilled in the art the best mode of carrying out the invention.
The details of the structure and/or function may be varied substantially without departing
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from the spirit of the invention.
Industrial Applicability
[0189] A cogeneration system 100 of the present invention is capable of efficiently
forcibly cooling a component which requires cooling and achieving self-sustainable
supply of water within the system. Therefore, the cogeneration system 100 is useful as
a power supply which actuates equipment which includes a component which requires
cooling and is located in a region which is not supplied with water easily from outside.
[0190] The equipment which is a combination of a component which requires forcible
cooling and a component which does not require the forcible cooling is not limited to the
above described BTS. For example, the equipment may be general electric power
consumption equipment, such as a server, a data center, ship, or communication
equipment for broadcast station. Therefore, the cogeneration system of the present
invention is applicable to these electric power equipment.
Reference Sings Lists
[0191] 1 SOFC hot module
2 drain tank
3 fuel processor system
4 fuel check valve
5 reformed gas check valve
6 hydrogenated desulfurization heat exchanger
7 total enthalpy heat exchanger
8 condensation heat exchanger
9 blower
10 ammonia absorption chiller
11 BTS
12 power management system (PMS)
13 SOFC cell
14 combustion section
15 vaporizer
16 reformer
17 current collecting member
18 trap
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20 first condensed water pump
21 second condensed water pump
22 anode
23 cathode
51 regenerative heat exchanger
52 rectification device
54 radiator
55 cooler
56 absorption device
57 storage container
58 cooling medium condensation heat exchanger
60 cooling section
61 power load
71 heating section
72 raw material passage section
72 fuel passage section
73 selective permeable membrane
100 cogeneration system
101 SOFC system
200 base station shelter
201 GRID
202 diesel generating apparatus
211 BTS
212 air conditioner
213 power management system (PMS)
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Claims
[1] A cogeneration system comprising:
a high-temperature operative fuel cell configured to generate electric power
through a power generation reaction by using a fuel supplied to the fuel cell and air
supplied to the fuel cell;
a reformer configured to generate a reformed gas which becomes the fuel,
through a reforming reaction between a raw material gas supplied to the reformer and a
steam supplied to the reformer, by utilizing power generation reaction heat generated in
the high-temperature operative fuel cell and combustion heat of unconsumed fuel;
a vaporizer configured to generate the steam to be added to the raw material gas
supplied to the reformer by utilizing the power generation reaction heat and the
combustion heat;
a cooling apparatus configured to cool a target by consuming a portion of the
power generation reaction heat and a portion of heat of an exhaust gas having the
combustion heat which remain after the reformer and the vaporizer have consumed the
heat, and cool the exhaust gas by consuming a portion of the heat; and
a condensation unit configured to cool the exhaust gas after the cooling
apparatus has consumed the portion of the heat owned by the exhaust gas to condense a
moisture contained in the exhaust gas to generate condensed water.
[2] The cogeneration system according to Claim 1,
wherein the condensation unit includes:
a first heat exchanger configured to heat the raw material gas to be supplied to
the vaporizer by utilizing heat of the exhaust gas after the cooling apparatus has
consumed the portion of the heat; and
a second heat exchanger configured to heat the air to be supplied to the solid
oxide fuel cell by utilizing the heat of the exhaust gas after the first heat exchanger has
utilized the heat and to condense the moisture contained in the exhaust gas to generate
the condensed water.
[3] The cogeneration system according to Claim 2,
wherein the first heat exchanger is a total enthalpy heat exchanger which heats
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the raw material gas to be supplied to the vaporizer by utilizing the heat of the exhaust
gas after the cooling apparatus has consumed a portion of the heat and humidifies the raw
material gas by the moisture contained in the exhaust gas.
[4] The cogeneration system according to Claim 1,
wherein the condensation unit includes a blower for air-cooling the exhaust gas
after the cooling apparatus has consumed a portion of the heat; and
wherein the blower cools the exhaust gas to condensate the moisture contained
in the exhaust gas to generate the condensed water.
[5] The cogeneration system according to any one of Claims 1 to 4,
wherein the vaporizer is configured to vaporize the condensed water by utilizing
the power generation reaction heat and the combustion heat to generate the steam.
[6] The cogeneration system according to any one of Claims 1 to 5,
wherein the cooling apparatus is an absorption cooling apparatus which causes a
cooling medium to be absorbed into an absorbing liquid and circulates the absorbing
liquid;
wherein the cooling medium has a lower boiling temperature than the absorbing
liquid; the cogeneration system comprising:
a third heat exchanger configured to exchange heat between the exhaust gas and
the absorbing liquid containing the cooling medium to separate the cooling medium from
the absorbing liquid containing the cooling medium;
wherein the absorbing liquid containing the cooling medium is vaporized by
heat attained by the heat exchange performed by the third heat exchanger.
[7] The cogeneration system according to Claim 6,
wherein the absorption cooling apparatus includes:
a rectification device configured to liquefy only the absorbing liquid from the
absorbing liquid having been vaporized and containing the cooling medium, to separate
the absorbing liquid from the cooling medium; and
a fourth heat exchanger configured to exchange heat between vaporized cooling
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medium which has been separated from the absorbing liquid by the rectification device
and the air to be supplied to the solid oxide fuel cell to liquefy the vaporized cooling
medium;
wherein the air heated by the heat exchange with the vaporized cooling medium
which is performed by the fourth heat exchanger is supplied to the high-temperature
operative fuel cell.
[8] The cogeneration system according to Claim 3, further comprising:
a water transporting unit configured to transport the condensed water generated
from the exhaust gas by the second heat exchanger, to the first heat exchanger;
wherein the condensed water transported by the water transporting unit is mixed
with the exhaust gas to generate the exhaust gas containing the condensed water as the
steam; and
wherein the first heat exchanger causes the steam contained in the exhaust gas to
be transferred to the raw material gas to heat and humidify the raw material gas.
[9] The cogeneration system according to Claim 8, further comprising:
a reduction reaction section configured to reduce a sulfur compound contained
in the raw material gas from a mixture gas containing a portion of the reformed gas
generated by the reformer and the raw material gas, to generate hydrogen sulfide; and
an adsorption section which adsorbs and removes the hydrogen sulfide generated
by the reduction reaction section;
wherein the reduction reaction section is supplied with the exhaust gas to be
supplied to the cooling apparatus, and a reaction temperature in the reduction reaction
section is maintained by the heat transferred from the exhaust gas.
[10] The cogeneration system according to any one of Claims 1 to 9, further
comprising:
a storage device configured to store the electric power generated in the
high-temperature operative fuel cell.
[11] The cogeneration system according to any one of Claims 1 to 10,
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wherein the cooling apparatus cools at least a component which requires cooling
as the target, in equipment actuated by the electric power generated in the
high-temperature operative fuel cell.
[12] The cogeneration system according to Claim 11,
wherein an upper limit value of a temperature to which the component which
requires cooling is cooled is predetermined; and
wherein the cooling apparatus cools the component which requires cooling to a
temperature lower than the predetermined upper limit value.
[13] The cogeneration system according to Claim 11 or 12,
wherein an amount of power generation in the high-temperature operative fuel
cell is controlled based on temperature information of the component which requires
cooling.
[14] The cogeneration system according to any one of Claims 1 to 10,
wherein the cooling apparatus cools the exhaust gas having been cooled by the
condensation unit, as the target, to condense the moisture contained in the exhaust gas to
generate the condensed water.